In recent years, adsorption refrigerators have been receiving attention in response to an increase in public demands for energy conservation, environmental protection, and the like. Main constituent elements of an adsorption refrigerator include a pair of adsorption reactors, a condenser, and an evaporator. Note that the adsorption reactor is also called an adsorption heat exchanger. Furthermore, the adsorption refrigerator has a vacuum pump for creating a vacuum in the adsorption reactor, the condenser, and the evaporator.
The condenser is provided above the pair of adsorption reactors arranged at the right and left. The evaporator is provided below the adsorption reactors. Furthermore, the adsorption reactor is provided with a first water circuit for circulating hot water or cooling water. The condenser and the evaporator are each provided with a second water circuit for circulating a refrigerant. The evaporator is provided with a third water circuit for circulating chilled water that cools a cooling target. The condenser is provided with a fourth water circuit for circulating cooling water.
In addition, the pair of adsorption reactors is provided with a switching valve for alternately circulating hot water and cooling water. Furthermore, the pair of adsorption reactors, the condenser, and the evaporator are each provided with an open/close valve, and the open/close valve allows a refrigerant vapor obtained by vaporizing a refrigerant, to pass through. Then, the adsorption refrigerator includes a control device that controls the vacuum pump and the open/close valve.
The adsorption reactor has an adsorbent such as silica gel or zeolite, which adsorbs and desorbs the refrigerant vapor, filled therein.
The space formed by the adsorption reactor, the condenser, and the evaporator is put into a reduced pressure with the vacuum pump. After that, the refrigerant vapor is obtained by the vaporization of the refrigerant through the use of the evaporator. At this time, heat is taken away from chilled water since the refrigerant is evaporated by vaporization, and thus the chilled water is cooled by the refrigerant. Then, the refrigerant vapor is adsorbed by the adsorbent in the adsorption reactor. The adsorbed refrigerant vapor is desorbed from the adsorbent by heating the adsorbent with hot water. The refrigerant vapor desorbed from the adsorbent is condensed into the refrigerant again with the cooling water through the condenser. The condensed refrigerant is transmitted to the evaporator through a pipe, and becomes vapor by vaporization again.
With the adsorption refrigerator described above, it is possible to generate chilled water with a temperature of approximately 9° C. by providing hot water with a temperature of approximately 80° C. and cooling water with a temperature of approximately 30° C. while maintaining the inside of the adsorption reactor, the condenser, and the evaporator under the reduced pressure. The temperature of 9° C. is cool enough to be capable of being sufficiently used for air conditioning.
The adsorption refrigerator is advantageous in that: the refrigerator consumes remarkably less electric power than an equivalent size of a general-type vapor-compression refrigerator employing a refrigerant such as alternative chlorofluorocarbon: natural working medium such as water can be used as the refrigerant; and hot water with a relatively low temperature can be effectively used. Namely, the adsorption refrigerator significantly reduces environmental load, provides enhanced safety, consumes less electric power, and exhibits high versatility.
In particular, hot water or cooling water to be used in the first water circuit does not come into contact with the adsorbent, the refrigerant and chilled water, and thus any material can be used as long as even a predetermined condition such as chemical stability is satisfied. In an extreme case, it is possible to use even seawater. Furthermore, the adsorption refrigerator can sufficiently use even low-temperature hot water which cannot be used in order to generate electric power in ordinary circumstances and which is difficult to be used in various types of industrial applications. The adsorption refrigerator can sufficiently use not only, for example, hot water utilizing exhaust heat obtained from factories but also hot water with a relatively low temperature such as hot water, obtained from waste incineration facilities or the like.
On the other hand, the only disadvantage is that the size of the adsorption refrigerator unavoidably increases in order to achieve high cooling performance. However, due to the advantages described above, which outweigh the disadvantage, the adsorption refrigerator has been significantly receiving attention in recent years.
In order to further improve the performance of the adsorption refrigerator as described above, a large number of engineers have been developing various techniques. One of the techniques includes a technique of making adsorption reactors into multiple stages.
In order to desorb the refrigerant vapor adsorbed by the adsorbent, hot water is necessary. The higher the temperature of the hot water is, in the shorter time the refrigerant vapor can be separated. For this reason, in the prior art, the adsorption refrigerator uses hot water with approximately 80° C. However, depending on locations or facilities where the adsorption refrigerator is installed, there may be cases where only hot water having a temperature that does not reach 80° C. is obtained. Namely, the lower the temperature of hot water that can be used is, the larger the application range of the adsorption refrigerator becomes. However, in the case where hot water utilized has a temperature lower than that of the prior art, the desorption capability of the adsorbent is lowered. Therefore, the amount of refrigerant vapor that the adsorption reactor adsorbs and desorbs becomes smaller than that in the prior art, and thus sufficient cooling effects cannot be obtained.
For these reasons, adsorption reactors are made into multi stages in order to ensure the amount of refrigerant vapor adsorbed and desorbed in the adsorption reactors so as to be equivalent to that in the conventional device even if hot water used has a low temperature. Namely, two stages or three stages of multi-staged adsorption reactors are provided between the condenser and the evaporator, and the refrigerant is caused to pass through the two stages or the three stages of the adsorption reactors. With the configuration, the reduction in the performance of the adsorption reactors in terms of adsorption of the refrigerant vapor, which takes place due to the use of the low-temperature hot water, can be compensated for. By making the adsorption reactor of the adsorption refrigerator into multiple stages as described above, it is possible to realize the adsorption refrigerator having a practical cooling capability even by using hot water of approximately 60° C.
Patent Literature 1 discloses details of technique of an adsorption refrigerator provided with two stages of adsorption reactors.